Ammonium polyphosphate-phosphonium bromide combinations as flame-retardants for propylene polymers

ABSTRACT

FLAME-RETARDANT COMPOSITIONS COMPRISING (A) A PHOSPHONIUM HALIDE HAVING THE FORMULA (R-)3P(+)(-R&#39;&#39;).BR(-) OR (R-)3P(+)-(CH2)2-P(+)(-R)3.2BR(-) WHEREIN R IS PHENYL OR 2-CYANETHYL AND R&#39;&#39; IS LOWER ALKYL, 2-CYANOETHYL, BENZYL OR BROMOBENZYL AND (B) AMMONIUM POLYPHOSPHATE AND POLYOFINS CONTAINING SAID COMPOSITIONS, ARE DISCLOSED.

United 8 States Patent O 3,649,591 AMMONIUM POLYPHOSPHATE-PHOSPHONIUM BROMIDE COMBINATIONS AS FLAME-RE- TARDANTS FOR PROPYLENE POLYMERS Robert William Murray, Lebanon, and Christos Savides, Piscataway, N.J., assignors to American Cyanamid Company, Stamford, Conn. No Drawing. Filed Oct. 29, 1970, Ser. No. 85,306 Int. Cl. C08f 45/04, 45/6'0; C091: 3/28 US. Cl. 260-41 10 Claims ABSTRACT OF THE DISCLOSURE Flame-retardant compositions comprising (A) a phosphonium halide having the formula wherein R is phenyl or 2-cya-noethyl and R is lower alkyl, 2-cyanoethyl, benzyl or bromobenzyl and (B) ammonium polyphosphate and polyolefins containing said compositions, are disclosed.

BACKGROUND OF THE INVENTION The production of resin compositions which are flameretardant is of considerable commercial importance in that such articles as castings, moldings, laminated articles, etc. are required, or at least desired, to be resistant to fire and flame and to possess the ability to endure heat without deterioration. Typical illustrations of applications of such compositions include castings for live electrical contacts which should not be ignited by flame or sparks, structural members such as pipes, wall coverings, wall paneling, windows, etc. and such items as ash trays, waste baskets, fibers and the like.

The use of certain additives for the purpose of reducing the flammability of various thermoplastic polymers is well known to those skilled in the art. Among the additives currently employed for such a use are various specific types of phosphonium bromide compounds. These phosphorus compounds are generally used either alone (US. 3,530,- 164 and 3,322,861) or in combination with other materials such as chlorinated hydrocarbons (U.S. 3,422,047 and 3,422,048) or 2,3-dicarboxy-5,8-endomethylene-5,6,7, 8,9,9 hexachloro1,2,3,4,4a,5,8,8a-octahydronaphthalene anhydride and its esters (US. 3,530,089 and 3,530,088).

SUMMARY We have now found that excellent flame-retarding properties can be imparted to propylene polymers by incorporating into the polymer a synergistic combination or mixture of (A) a phosphonium bromide having the formula I R31 R-Brwherein R is phenyl or 2-cyanoethyl and R is lower alkyl, 2-cyanoethyl, benzyl or bromobenzyl, or the formula RaP-CH2CHg-PR3-2Bl" wherein R is as defined above, and (B) ammonium polyphosphate.

3,649,591 Patented Mar. 14, 1972 The novel synergistic combination of phosphonium bromide and ammonium polyphosphate provides improved flame-retardance over additives of the prior art and, additionally, generally provide this superior result at lower concentrations than previously believed necessary for known additives. The results shown by the use of the above-disclosed novel flame-retardant combinations are surprising and unexpected in that the combinations provide a greater degree of flame-retardancy than one would expect from the results shown by the use of the components individually, i.e. they are synergistic.

DESCRIPTION OF THE INVENTION INCLUDING PREFERRED EMBODIMENTS As mentioned above, the first critical component of our novel flame-retardant compositions is a compound represented by either Formula I or Formula II, above. These compounds are generally well known in the art, as are methods for their preparation, as represented by US. Pat. No. 3,005,013 and those set forth hereinabove, which patents are hereby incorporated herein by reference.

The second critical component of our novel flame-retardant compositions in an ammonium polyphosphate. These compounds are also well known in the art as exemplified by U.S. Pat. Nos. 3,423,343 and 3,513,114, which patents are also hereby incorporated herein by reference. These ammonium polyphosphates are generally substantially water-insoluble and possess a plurality of P-O-P type linkages. They can be represented by the formula wherein n is an integer having an average value greater than 10, m/n is between about 0.7 and about 1.1 and the maximum value of m is equal to n+2. They are straight or branched chain structures having nearly all the nitrogen present therein as ammonical nitrogen. The average numerical value of n, using end group titration after acid formation, is from about 20-400, while using the light scattering method, the average weight value of n is above about 500, preferably 500100,000 and especially preferably 1000-30,000. The ammonium polyphosphates exhibit diiferent crystalline forms but are also found in the non-crystalline or amorphous form also.

The combination of phosphonium bromide and ammonium polyphosphate is useful as a flame-retardant when incorporated into propylene polymers in a flame-retarding amount, i.e. at least about 5%, by weight, preferably from about 5% to about 25%, by weight, based on the weight of the polymer. The ratio of phosphonium bromide to ammonium polyphosphate should range from about 2:1 to about 1:2, respectively.

The propylene polymers rendered flame-retardant by the incorporation therein of our novel combination include the homopolymer of propylene and copolymers of propylene and olefin comonomers which possess from 2- 4 carbon atoms, inclusive, such as ethylene, butylene, isobutylene etc.; the copolymers containing 50-90% of propylene, by weight.

The novel flame-retardant combinations claimed herein may be added to the various propylene polymers, as such, or as individual components, by any known method. That is to say, the flame-retardant components may be added 3 to the polymer, as such, or in combination by (1) mill ing the polymer and the components on, for example, a two-roll mill, in a Banbury mixer, etc., by (2) molding the components and the polymer simultaneously, by

In addition to the superior results exhibited above by the synergistic combination of the phosphonium bromide and ammonium polyphosphate, -we have also discovered that these unique combinations can be further modified (3) extruding the polymer and components or by (4) 5 by the incorporation therewith, into the propylene polymerely blending all the materials together in powder or mer, of various oxides and/or carbonates. The addition liquid form and thereafter forming the desired ultimate of these oxides etc. results in the production, when the product. Additionally, the flame-retardant components or combination is added to propylene polymers, of products combination may be added during the production of the which are not only flame-retarded but also rendered non- P during the monomer Polymerization, P dripping. By non-dripping is meant that when the provided, however, that the catalyst, etc. other conditions and ylene polymer is burned, the material does not drip, other ingredients of the polymerization system are inert either as a burning or a molten mass. This property is thereto. rapidly becoming a requirement of plastics which are to It is also within the scope of the instant invention to be used for various applications such as those mentioned incorporate such ingredients as plasticizers, dyes, pigments, above. heat and light stabilizers, antioxidants, antistatic agents, The oxides or carbonates are added to the propylene photochromic materials and the like into the flame-repolymer in an amount ranging from about 0.25% to about tarded propylene polymer compositions claimed herein. 5%, by weight, based on the weight of the polymer. The The following examples are set forth for purposes of manner in which the oxide or carbonate is added is not illustration only and are not to be construed as limitations critical and it can be added to the polymer before, along on the present invention except as set forth in the apwith or after the phosphonium bromide-ammonium polypended claims. All parts and percentages are by weight phosphate combination. Amounts higher than about 5% unless otherwise specified. In the examples, the additives, are generally undesirable since they appear to cause the in the concentrations indicated, were either (1) dry blended propylene polymer to burn more readily, behaving as if with the propylene polymer, extruded at 420 F. and there was no flame-retardant present. chopped into pellets and then injection molded at 400- It is not completely understood why these oxides or 450 F. into bars 5" x 0.5" x 0.25" or (2) dry blended carbonates function within relatively narrow limits to with the propylene polymer and extruded through the prevent dripping of the propylene polymer on burning orifice of a melt-index apparatus (described in ASTM-D- and We do not wish to be held to any particular theory 12338-65T) at 250 G. into a 5-7" cylindrical extrudate. in t regard. Nevertheless, we have nd t at alkali The flammability of the injection molded bars was measmetal carbonates such as sodium carbonate, potassium ured according to ASTM-D-63S or Underwriters Laboracarbonate etc.; alkaline earth metal oxides such as barium tory Test UL-94 while that of the extruded cylinders was oxide, magnesium Oxide alkaline earth metal Ca bonmeasured using a modified ASTM-D-635 method as ates such as magnesium carbonate, calcium carbonate etc.; described in the above-mentioned patents. The ammonium Group IV-A metal oxides such as silicon dioxide, stannic polyphosphate used was a commercially available maoxide, etc.; titanium dioxide; zinc oxide; aluminum oxide; terial having a phosphorus Weight percent of 32 and an antimony oxide and the like can be used. While some of ammonical nitrogen to phosphorus molar ratio of 0.92. the mpounds function at low concentrations, e.g. about The results are set forth in Table 1, below. 0.25%, but not at about 5.0%, others perform at the TABLE I Phosphonium bromide Percent ammonium Formula polyphos- Propylene Flammability Flammability Example No. R Percent phate polymer test used rating Free burning. Do. do. Self-extinguishing. Modified ASTM Free-burning.

D-635. 5 I -do do 2.5 2.5 ....do do Beilf'extinguishn 6 20 .do do Fre -buring; d0-. Do.

.. Bell-extinguishing. Free-burning. Seili-extinguishn ....-do .Z-eyanoethyi 10 do do Free -burning.

.. -do do 5 5 ...do do sellf-exgingulshl1 2-eyanoethyl Benzyl 10 do do Fregburning. ...do do 5 5 ...do Stilt-extinguish- I1 Free -burning. Self-extinguishing. Free-burning. 7.5 7.5 -do do Stilt-extinguish- 11 10 do do 1 30.

.. Stilt-extinguish- 11 o-Bromebenzyl Fre -burning. do Belg-extinguish- Z-cyanoethyl Methyl 10 do do Frag-burning. .-do do 5 5 do do Stilt-extinguish- I! .do-..-.-.-..-........ do Free -burning.

7.5 .....do ..do Self-extinguishl'l Ethylene propylene -....do Free -burning.

copolymer (20/80). 5 do do Seth-extinguish- 15 do ..do Fra -burning.-

higher level only. In all cases, however, the oxides or carbonates function to prevent dripping in a synergistic manner with the flame-retardant combination at a concentration within the above range.

The examples below clearly illustrate the unique effect afforded by the use of the oxide or carbonate in conjunction with'the flame-retardant combinations of Examples l-29, above. The tests used, percentages, manner of in- 6. A composition according to claim 4 wherein said (A) is tetrakis(Z-cyanoethyl)phosphonium bromide.

7. A composition according to claim 4 wherein said (A) is ethylenebi s[tris(2-cyanoethyl) ]phosphonium bromide.

8. A composition according to claim 1 containing, in addition thereto, (C) from about 0.25 to about 5.0%, by weight, based on the weight of the polymer to which the composition is to be added, of a compound selected corporation, etc. conform to those enumerated above. The results are set forth in Table H, below.

from the group consisting of (1) alkali metal carbonates, (2) alkaline earth metal carbonates, (3) alkaline earth TABLE II Phosphonium bromideammonium pol'yphosphate flame-retnrded polymer oi Flammability Example No. Oxide or carbonate Percent test used Flammability rating '3 Zine oxide 1.0 UL-94 Self-extinguishing non-dripping. 3 Barium oxide 1. UL-94 Do. 3 Stannic oxide 5.0 UL-94 Do 3 Aluminum oxide 5.0 UL-94 Do 3 Sodium carbonate 1.0 TIL-94 Do 3 Magnesium carbonate.. 1.0 UL94 Do 3 Magnesium oxide 1.0 UL-94 Do 3 Silicon dioxide. 0.25 UL-94 Do 3 d 0.5 UL-94 D 13 1.0 UL-94 Do *3 2.0 (IL-94 Do 13 2.0 UL-94 Do 3 5.0 UL-94 Do 5 1.6 UL-94 Do 3 2.5 UL-94 D0 12 1.6 UL94 Do 12 4.5 UL-94 Do 14 1.0 IL-94 Do 16 0.57 [TL-94 D0 20 4.0 UL-94 Do 22 2.5 TIL-94 Do 24 3.0 UL-94 Do 26 Stannic oxide. 3.0 UL-94 Do 28 Silicon dioxide 1.0 UL-94 Do I 10% oi each component. I t

We claim: metal modes, (4) Group IV-A metal oxides, (5) titanium 1. A flame-retardant composition comprising (A) a dioxide, (6) 21116 oxide, (7) aluminum oxide and (8) compound having the formula antimony oxide.

. 3 9. A composition according to claim 8 wherein (C) is silica dioxide. 10. A flame-retarded composition comprising a prowherein R is phenyl or Z-cyanoethyl and R is lower alkyl, pylene polymer having incorporated therein a flame-retard- 2-cyanoethyl, benzyl or bromobenzyl and (B) ammonium ing amount of the composition of claim 8. polyphosphate, the ratio of (A) (B) ranging from about 231,.to about 1:2, respectively. 1

2. A composition according to claim 1 wherein (A) is ttgakis (iZ-cyanoethyl) phosphonium ;bromide.

3. A composition according to claim 1 wherein (A) is ethyleneiiis[tris(2-cyanoethyl) ]phosphonium bromide.

4. A flame-retarded composition comprising a propylene polymeri having incorporated therein a flame-retarding arnpuntof the composition of claim 1.

5. A- composition according to claim 4 wherein said 55 propylene polymer is polypropylene.

References Cited UNITED STATES PATENTS 3,562,197 2/1971 Sears et a1. 252--8.1

MORRIS LIEBMAN, Primary Examiner J. H. DERRINGTON, Assistant Examiner US. Cl. X.R.

106-15FP; 2528.l; 260-45.7 P, 45.75, 45.9 R 

